The corpus luteum of the menstrual cycle is maintained after conception as the corpus luteum of pregnancy. This structure secretes different steroids than the corpus luteum of the cycle and also secretes relaxin. The pattern of relaxin secretion during pregnancy will be obtained by peripheral blood samples. Altered secretion of relaxin in pathological states of pregnancy will be observed. We will attempt in vitro to convert the corpus luteum of the menstrual cycle to a relaxin secreting structure using a cell culture system. We will also determine the effects of various hormones such as HPC, HCG, prolactin and CAMP on progesterone and relaxin secretion in both the cycle and pregnancy corpus luteum.